The invention relates to an induction furnace for melting and casting purposes, which has a closed crucible pot with a bottom part and a gas-tight cover releasably superimposed thereon, the whole with a vertical axis. The furnace has a crucible which is contained in the crucible pot and has a likewise vertical axis and is surrounded by an induction coil; and it has an ascending tube reaching into the crucible, through which the crucible can be emptied by gas pressure into a casting apparatus.
The enclosed crucible pot is suitable for operating the crucible under a vacuum and/or protective gas, the protective gas serving, after the melting operation and an appropriate treatment of the melt, to force the latter out of the furnace.
While the teeming of so-called open induction furnaces operated in the atmosphere causes no appreciable problems because the crucible along with the induction coil is mounted for tipping in a furnace frame, teeming presents difficulties in the case of closed induction furnaces, especially vacuum induction furnaces.
Vacuum induction furnaces are known in which a crucible with an induction coil surrounding it is disposed for tipping in a stationary crucible pot. This crucible pot, however, must be of such great dimensions as to provide enough space for the crucible and the induction coil to be tipped. But with the pot volume so large, the teeming time is lengthened and the vacuum pumping expense is increased. Moreover, a complicated coaxial connection between the induction coil and a transformer standing outside of the furnace is needed. This coaxial connection must permit the tipping of the crucible with the induction oil in spite of heavy currents, and likewise the absolutely leak-proof management of the cooling water running through the induction coil.
To remedy these problems vacuum induction furnaces have already been created in which the crucible pot is tippable with all its auxiliary equipment. If in this case the melt has to be teemed with the exclusion of air, such a furnace design calls for a jointed and hermetically sealed teeming spout which involves heat losses from the melt, so that only a considerably overheated melt can be teemed. But this again has harmful effects on the ceramic lining of the teeming spout.
The so-called "ascending tube," which in itself is likewise known, has in this regard created a promising remedy; connecting it to the pot cover or carrying it through the pot cover, however, has greatly hampered any continuous or quasi-continuous operation of the melting and casting furnace. Upon each recharging of the furnace the crucible pot has to be flooded and the pot cover has to be lifted upward to a considerable extent in order to be able to swing the correspondingly long ascending tube over the top edge of the bottom part of the pot.
It is therefore the aim of the invention to devise an induction furnace of the kind described above, which will permit continuous and quasi-continuous operation and permit measurements, analyses and the like to be performed while operation is in progress.